Access systems, such as motorized lifts, have been used to transport people and cargo. These access systems include platforms, ramps, moving seats, movable steps, and the like, which may be attached to stationary structures, such as buildings and loading docks, or mobile structures such as vehicles. Access systems have been used to provide disabled individuals access to structures that traditionally were accessible only via steps or stairs, or required an individual to step over or across an obstacle. For example, motorized lifts have been used to allow disabled individuals to enter and exit vehicles. In another example, motorized lifts have been used to load and/or unload stretchers from vehicles, such as ambulances. Motorized lifts have also been used on loading docks and trucks to allow cargo to be loaded, unloaded or otherwise moved.
When an access system is installed in a vehicle that includes a power sliding door, the access system may be configured to interface with the power sliding door system of the vehicle. As understood in the industry, components, such as power sliding doors, that are installed in the vehicle by the vehicle manufacturer are referred to as OEM components. The OEM power sliding door system opens or closes the door when it receives a request to do so (a “door operation request”). Some power sliding door systems include a body control unit, a door control unit, a receiver, various door switches, and a data bus. The body control unit, door control unit, receiver and at least some of the door switches are in communication with the vehicle's data bus, which enables various vehicle components to communicate with each other, for example, to receive a signal from a user indicating that the user wants to open or close the door (a “door operation request”).
Depending upon the specific vehicle, the user may communicate a door operation request to the power door system by pulling on a door handle of the vehicle, depressing one of the door switches located throughout the vehicle, or by pushing a button on a keyless entry device. If the door operation request is produced by the keyless entry device, the request is often received by the remote receiver, transmitted to the body control unit, and if appropriate, communicated to the door control unit over the data bus. If the door operation request is produced by movement of the door handle, the door operation request is often communicated directly to the door control unit, but will only be executed (e.g. by opening or closing the door) if appropriate vehicle conditions are detected by the body control unit. If the door operation request is produced by movement of one of the door switches located throughout the vehicle, depending upon the specific switch, the door operation request may be communicated directly to the body control unit, or may be communicated to the body control unit or to the door control unit via the data bus. Once the door operation request reaches the body control unit or the door control unit, the door operation request is managed in the manner discussed above.
As mentioned, door operation requests will only be executed if the body control unit determines that vehicle conditions are satisfactory to allow operation of the door. For example, the body control unit may receive signals via the data bus indicating the status of the transmission position, speed and door lock position of the vehicle. If the body control unit determines that vehicle conditions are acceptable (e.g. the vehicle is in park), the body control unit communicates an authorization command to the door control unit so that the door control unit will operate to move the door in response to receiving a door operation request. The door control unit operates to move the door by supplying electrical power to motors, clutches and actuators that unlatch, and open or close the door.
When access systems are installed in vehicles with OEM power sliding door systems, the access system must be configured such that operation of the ramp by the access system and operation of the door by the power sliding door system are coordinated to prevent interference between the door and the ramp. One method of preventing such interference is installing the access system in a manner that interrupts the door operation commands sent from the body control unit to the door control unit. This method requires the access system to be in communication with the data bus of the power sliding door system, either directly or through a gateway. While these methods have proven effective in the past, vehicle manufacturers are becoming less willing to allow installers of vehicle access systems to modify or otherwise communicate with or on the vehicle data bus.